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ATP and glutamate are released from separate neurones in the rat medial habenula nucleus: frequency dependence and adenosine‐mediated inhibition of release
Author(s) -
Robertson Susan J.,
Edwards Frances A.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.691bp.x
Subject(s) - glutamate receptor , adenosine , stimulation , glutamatergic , purinergic receptor , chemistry , biophysics , adenosine a1 receptor , adenosine triphosphate , neuroscience , biology , adenosine receptor , receptor , biochemistry , agonist
1 ATP and glutamatergic synaptic currents were compared in slices of rat medial habenula nucleus using whole‐cell patch‐clamp techniques. 2 In most cells low voltage stimulation resulted in glutamatergic responses and not purinergic responses. In five cells where ATP currents could be stimulated with low voltages, wash out of glutamate antagonists did not reveal evoked glutamate currents. Spontaneous glutamate currents confirmed washout of antagonist. 3 Modulation of release probability of glutamate and ATP, assessed by changes in failure rate of synaptic currents, was compared under conditions of different stimulation frequencies and in the presence of adenosine agonists and antagonists. 4 ATP release, but not glutamate release, was shown to be modulated by increased stimulation frequency which resulted in inhibition of ATP release via A 2 ‐like adenosine receptors. A 1 receptors caused inhibition of both ATP and glutamate release. 5 Endogenous adenosine inhibited glutamate release via A 1 receptors but only inhibited ATP release via A 2 ‐like receptors. 6 Attempts to inhibit the degradation of ATP to adenosine did not alter the frequency dependence of the failure rate. 7 We conclude, from the direct demonstration and from the differences in pharmacology and frequency dependence of the modulation of release, that ATP and glutamate responses are due to release from separate neurones.